Recirculating pneumatic separators are commonly used in the separation of tobacco products, such as the separation of threshed tobacco leaves from the heavier tobacco parts such as stems. Conventional recirculating pneumatic separators typically include a winnower as a feed device that imparts a substantial velocity to the particles of material to be fed to the separator. The winnower consists of a rotary impeller with a plurality of vanes rotating at extremely high speeds, typically 500 to 800 rpms. The rapidly rotating vanes physically contact the particles of material to be separated and thereby impart a substantial velocity to the material.
Unfortunately, several negative consequences result from operating a winnower at these high rates of rotation. The direct physical contact of the high speed vanes with the product leads to substantial degradation of the product. The yield of a conventional recirculating pneumatic separator is thus negatively affected by the product degradation. Furthermore, in the processing of tobacco, it is absolutely critical to avoid introducing any foreign matter into the tobacco. Winnowers, running at a high revolution rate, break down frequently and lose portions of their vanes into the tobacco product. Introducing the broken portions of the winnower into the tobacco processing stream is a critical and unacceptable problem in the processing of tobacco.
What is needed is an improved method of separating threshed tobacco leaves from the heavier tobacco parts. The improved separation device and method should preferably reduce the amount of product degradation thereby having a positive effect on separator yield. The method should also eliminate the possibility of contaminating the tobacco product with broken portions of the separator machinery. These improvements are realized by the feed device of the present invention, which eliminates the winnower as a piece of machinery in the separation of tobacco products.